With the advent of computers in homes and businesses, there has been a proliferation of various database to be utilized therewith. At the present time each database, whether it contains information concerning news, science or business etc., will transmit the data in either a bit synchronous or character asynchronous format. In a synchronous data transmission, each character consists of either 5, 6, 7 or 8 information bits depending upon the code structure. There are no start and stop bits. Rather, character timing is derived through synchronizing characters at the beginning of each message or block of data. And an asynchronous data transmission is one wherein each character also consist of either 5, 6, 7 or 8 information bits, depending upon the code structure. These information bits are preceded by a start bit (zero condition) and followed by one or more stop bits (one condition) to synchronize a receiver with a transmitter for receipt of each character. A parity bit is sometimes included to detect errors.
Communication with a database is usually obtained through use of a data terminal. Heretofore, these terminals were manually reconfigured as appropriate each time a new database was called by the user who was knowledgeable as to whether the data transmission was in a bit synchronous or a character asynchronous mode. Often times today a user of a terminal is not familiar with the various ways of reconfiguring a terminal, and may not be familiar with the transmission format of the database. This is true since a large number of the users of terminals are now found in areas that are not technical or scientific in nature. Thus, it is important that the terminals be user friendly, i.e., easy to use by people who are not familiar with how terminals receive and transmit data.
Accordingly, it is desirable for a terminal to automatically determine whether the data being received is in a character asynchronous or bit synchronous format. It is also desirable for the terminal to be able to automatically adapt itself to the appropriate mode of operation. A terminal capable of these operations is easier to use in interfacing with new and different databases wherein the format of the data transmission is not readily known. An example of a database employing the first type of transmission is the Source, a home-based personel computer service of Reader's Digest.RTM., which employs a character asynchronous format for its data transmission. An example of the second type of database is that provided by Viewdata Corporation of America's Viewtron.RTM. service. The database employs a bit synchronous format for its data transmission.
As additional databases with unknown formats of transmission become accessible from a terminal, the importance of automatically determining the format of transmission increases.